Method of monitoring a surface feature and apparatus therefor

ABSTRACT

Dimensions of a surface feature are determined by capturing an image of the surface feature and determining a scale associated with the image. Structured light may be projected onto the surface, such that the position of structured light in the captured image allows determination of scale. A non-planar surface may be unwrapped. The surface may alternatively be projected into a plane to correct for the scene being tilted with respect to the camera axis. A border of the surface feature may be input manually by a user. An apparatus and system for implementing the method are also disclosed.

FIELD OF THE INVENTION

The invention relates to a method of monitoring a surface feature and anapparatus for performing such monitoring. The method and apparatus mayfind application in a wide range of fields from industrial applicationsthrough to medical or veterinary applications such as monitoringdermatological surface features such as wounds, ulcers, sores, lesions,tumours, bruises, burns, psoriasis, keloids, skin cancers, erythema etc.

BACKGROUND TO THE INVENTION

Various techniques have been used to monitor wounds, ulcers, sores,lesions, tumours etc. (herein referred to collectively as “wounds”) bothwithin hospitals and outside hospitals (e.g. domiciliary based care,primary care facilities etc.). Typically these wounds are concave and upto about 250 millimetres across. Manual techniques are typicallylabour-intensive and require examination and contact by skilledpersonnel. Such measurements may be inaccurate and there may besignificant variation between measurements made by different personnel.Further, these approaches may not preserve any visual record for reviewby an expert or for subsequent comparison.

A number of techniques for the automated monitoring of wounds have beenproposed; see for example U.S. Pat. No. 6,101,408, U.S. Pat. No.6,873,340, U.S. Pat. No. 4,535,782 and U.S. Pat. No. 5,967,979. A commonapproach is to place a reference object next to the wound and determinethe size of the wound utilising the scale of the reference object. It isoften undesirable to place a reference object near to a wound and thisrequires an additional cumbersome step for a user and riskscontamination of the wound. Further, when the target is not in the planeof the wound, or if the wound is not planar, there will be errors in anyarea calculation.

WO 2006/078902 discloses a system in which the scale of a captured imageis determined using a laser triangulation sensor. The distance of thecamera from a patient's skin is determined using the position of a laserspot in the image. Only a single laser spot is used and the laser isused only in a simple distance measurement.

Systems utilising stereoscopic vision and automated boundarydetermination are known but they are expensive, complex, bulky andrequire significant computational power. Further, automatedidentification of the boundary of a wound-may be inaccurate andvariable. U.S. Pat. No. 6,567,682 and US2005/0084176 use stereoscopictechniques and automated wound boundary determination requiringintensive processing and bulky equipment.

Other systems, such as that described in US2004/0136579, require thecamera always to be positioned with a guide against the patient's skin.While this consistently positions the camera a desired distance from thesurface to be photographed and therefore sets the scale of the image, itis unwieldy and requires undesirable contact with the skin, riskingcontamination of the wound.

US2005/0027567 discloses a system in which a medical professional mayenter patient information into a portable computing device. A nurse mayalso photograph the patient's wounds, these photographs becoming part ofthe patient's record. However, use of this image data is limited and thecomputing device is effectively used simply to allow notes to be taken.

It is an object of the invention to provide a simple, inexpensive andrepeatable method that does not require a scale reference object to beemployed and that may be performed at remote locations or to at leastprovide the public with a useful choice. It is a further object of theinvention to provide an apparatus that is simple, portable, inexpensiveand easy to use or which at least provides the public with a usefulchoice.

SUMMARY OF THE INVENTION

There is thus provided a method of producing a projection of anon-planar surface feature comprising:

-   -   a. projecting structured light onto the surface feature;    -   b. capturing an image including the surface feature;    -   c. determining the three-dimensional coordinates of structured        light elements within the image; and    -   d. unwrapping the image based on the three-dimensional        coordinates of the structured light elements to produce a planar        projection of the surface feature.

According to a further embodiment there is provided a method ofdetermining the area of a non-planar surface feature comprising:

-   -   a. projecting structured light onto the surface feature;    -   b. capturing an image including the surface feature;    -   c. determining the three-dimensional coordinates of structured        light elements within the image;    -   d. determining scale attributes for regions of the image on the        basis of the three-dimensional coordinates of the structured        light elements; and    -   e. determining the area of the surface feature by scaling        regions of the surface feature based on the scale attributes.

According to another embodiment there is provided a method of producinga projection of a surface feature comprising:

-   -   a. capturing an image of a surface feature;    -   b. determining from the image the coordinates of a plurality of        points of the surface feature in three-dimensional space;    -   c. determining a plane in which at least a subset of the        coordinates lie; and    -   d. projecting the image onto the plane to produce a transformed        image.

According to a further embodiment there is provided a method ofdetermining at least one dimension of a surface feature, including:

-   -   a. capturing an image including a surface feature;    -   b. determining a scale associated with the image;    -   c. manually inputting at least part of an outline of the surface        feature; and    -   d. determining at least one dimension of the surface feature        using the manually input outline data.

According to another embodiment there is provided an apparatusincluding:

-   -   a. a camera for capturing an image including a surface feature;        and    -   b. a portable computing device including:        -   i. a display configured to display the image and to allow a            user to manually input at least part of an outline of the            surface feature; and        -   ii. a processor configured to determine a scale associated            with the image and to determine at least one dimension of            the surface feature using the manually input outline data.

According to a further embodiment there is provided a portable apparatusincluding:

-   -   a. a camera for capturing an image of a surface feature;    -   b. a portable computing device including a processor adapted to        determine a scale associated with the image; and    -   c. a positioning module allowing the position of the apparatus        to be determined.

According to another embodiment there is provided a healthcare apparatusincluding:

-   -   a. a camera for capturing an image of a surface feature on a        patient;    -   b. one or more auxiliary sensors for determining a physical or        chemical parameter associated with the patient; and    -   c. a portable computing device configured to receive image data        from the camera and output from the auxiliary sensors, including        a processor adapted to determine a scale associated with the        image.

According to a further embodiment there is provided an apparatusincluding:

-   -   a. a camera for capturing an image including a surface feature;        and    -   b. one or more structured light projectors configured to project        structured light onto the surface, the structured light        including two or more structured light components, each        projected at a different angle to the camera's optical axis.

DRAWINGS

The invention will now be described by way of example with reference topossible embodiments thereof as shown in the accompanying figures inwhich:

FIG. 1 shows the principle of operation of an apparatus according to oneembodiment;

FIG. 2 shows an image of a surface feature with a single stripeprojected onto the surface feature;

FIG. 3 a shows an image of a surface feature with cross hairs projectedonto the surface feature;

FIG. 3 b shows a cross-sectional view of a wound;

FIG. 4 shows an image of a surface feature with a series of dotsprojected onto the surface feature;

FIG. 5 shows one embodiment employing a personal digital assistant (PDA)for performing methods of the invention;

FIG. 6 shows a bottom view of a Tablet PC and 3-D camera;

FIG. 7 shows a top view of the Tablet PC and 3-D camera of FIG. 6.

FIG. 8 shows an alternative apparatus and method;

FIG. 9 shows an image illustrating a method of using the apparatus ofFIG. 8;

FIG. 10 shows an apparatus according to a further embodiment; and

FIG. 11 shows a system according to another embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1 the general principle of operation of a firstembodiment of the invention will be described. A camera 1 has an opticalaxis 2 and an image capture region 3. Laser 4 is disposed in a fixedangular relationship to optical axis 2 so that the fan beam 5 isdisposed at angle α to optical axis 2. In this embodiment laser 4generates a single stripe 6. Alternatively a laser projecting a singledot could be used. The camera 1 is preferably a high resolution digitalcolour camera. Optionally, an illumination means (such as a white LED 44for low power applications) can be used to give relatively constantbackground lighting.

In use the assembly of camera 1 and laser 4 is directed so that opticalaxis 2 is aligned with the central region of wound 7. Laser 4 projectsstripe 6 across wound 7 and the image is captured by camera 1. It willbe appreciated that due to the fixed angular relationship of the laserfan beam 5 and the optical axis 2 that the distance of points of stripe6 from camera 1 may be determined: the distance of points of stripe 6along the x-axis shown in FIG. 1 is directly related to the distance ofthe point from camera 1.

In a first embodiment the assembly of camera 1 and laser 4 may bepositioned above wound 7 so that stripe 6 is aligned with optical axis2. This may be achieved by aligning cross hairs (or a dot) in the centreof a display screen displaying the image with the centre of wound 7 andstripe 6. In this way the camera is positioned a known distance awayfrom the centre of wound 7 and so a scale can be determined.

The area of a wound may be calculated by calculating the pixel area ofwound 7 from a captured image and multiplying by a known scaling factor.This technique may be effective where camera 1 can be oriented normal tothe wound 7 and where wound 7 is generally planar. This technique offersa simple solution in such cases. However, many wounds are not generallyplanar and images may be taken at an oblique angle. In such cases thisapproach may not provide sufficient accuracy and repeatability due tothe camera axis not being perpendicular to the wound and significantvariation in the distance from the camera to the wound from thatassumed.

In a second embodiment an image may be captured in the same fashionexcept that the stripe need not be aligned with the optical axis of thecamera. An image as shown in FIG. 2 may be obtained. Points 9 and 10,where the outline 8 of wound 7 intersects stripe 6, may be used tocalculate scale. From the locations of points 9 and 10 in the image 3their corresponding (x, y, z) coordinates can be obtained using theknown relationship of the laser-camera system. Thus a scale factor maybe determined based on the x,y,z coordinates of points 9 and 10 to scalethe area 7 to produce a scaled value. Whilst this technique does notrequire a user to align the stripe with the optical axis it stillsuffers from the limitations of the technique described above.

In one embodiment laser 4 projects structured light in the form of lasercross hairs onto the image capture area. An image captured according tothis embodiment is shown in FIG. 3 a. The laser stripes 11 and 12captured in the image may be identified automatically based on colour,light intensity etc. The outline 13 is preferably user defined bydrawing the outline on a touch display screen displaying the image. Theimage points 14, 15, 16 and 17 where cross hairs 11 and 12 intersectwith outline 13 may be automatically determined. From these points theircorresponding (x, y, z) coordinates can be obtained as above. Thesethree-dimensional coordinates may be utilised to determine the best-fitplane through all points. The best-fit plane will generally be the planehaving the minimum sum of squared orthogonal distances from the pointsto the plane. The image may then be projected onto this plane using, forexample, an affine transformation. The resulting image is now scaledlinearly and orthogonally. The area within outline 13 may then becalculated from this transformed image. Any number of laser stripes maybe used and these stripes may intersect with each other or not.

This approach has the advantage that it provides correction where animage is not taken normal to a wound. Determining the area within a twodimensional outline rather than in three dimensional space also reducesthe computational load.

A wound depth measurement may also be derived as will be explained inconnection with FIG. 3 b. The point 18 of greatest depth b from best-fitplane 19 may be determined iteratively or by other methods. This may bedetermined for an individual point along one of the cross hairs 11,12 orfor a group of points.

Utilising this information standard wound measurements may be made. Theso-called “Kundin area” may be calculated by obtaining the maximumlinear dimension of the wound and the short axis (orthogonal to the longaxis) of the outline and multiplying the product of these measurementsby π/4. The so-called “Kundin volume” may be calculated from the productof the two diameters, the maximum depth and a factor of 0.327. Thedimensions may be determined and the volume calculated by a localprocessor. Various other algorithms may be used to calculate woundvolume as appropriate for the circumstances.

Referring now to FIG. 4 another implementation is shown. In this case aseries of three laser dots 31, 32 and 33 are projected instead of one ormore laser stripe. The laser dots are projected in a diverging patternso that as the device is moved towards or away from the surface featurethe spacing between the dots may be scaled so that they may be alignedwith the outline of the wound 30. This approach has the advantage thatthe intersection between the stripes and the wound outline does not needto be determined as in previous embodiment. Further, the plane passingthrough the three points may be easily calculated. A further point 34may be provided for depth calculation. Point 34 will preferably beplaced at the position of maximum wound depth.

The outline of the wound may be determined utilising image processingtechniques. However, the results of such techniques may be variabledepending upon image quality, available processing capacity and theoptical characteristics of the wound. According to a preferredembodiment the outline is input by a user.

Apparatus for performing the method may take a variety of forms rangingfrom a stationary system (having a stationary camera or a handheldcamera connected wirelessly or by a cable) to a fully portable unit.Portable units in the form of PDAs, cell phones, notebooks, ultramobilePCs etc. including an integrated or plug-in camera allow greatflexibility, especially for medical services outside of hospitals.Referring now to FIG. 5 an apparatus for implementing the inventionaccording to one exemplary embodiment is shown. The apparatus consistsof a PDA 20 including a camera, such as a Palm or HP iPaQ, having across hair laser generator 21 which projects cross hairs at an angle tothe optical axis of the PDA camera (as shown in FIG. 1). For thisembodiment the cross hair laser generator may be offset from the cameraby about 50 millimetres and disposed at an angle of about 30° to theoptical axis of the camera. An image is captured by the camera of thePDA and displayed by touch screen 22. A user can draw an outline 24about the boundary of the wound 25 using input device 23 on touch screen22. The apparatus may allow adjustment of outline 24 using input device23.

In one embodiment placing input device 23 near outline 24 and draggingit may drag the proximate portion of the outline as the input device 23is dragged across the screen. This may be configured so that the effectof adjustment by the input device is proportional to the proximity ofthe input device to the outline. Thus, if the input device is placedproximate to the outline the portion proximate to the outline will beadjusted whereas if the input device is placed some distance from theoutline a larger area of the outline will be adjusted as the inputdevice is dragged.

Utilising manual input of the outline avoids the need for complex imageprocessing capabilities and allows a compact portable unit, such as aPDA, to be utilised. Further, this approach utilises human imageprocessing capabilities to determine the outline where automatedapproaches may be less effective.

Once an image is captured it may be stored by the PDA in a patientrecord along with measurement information (wound area, wound depth,wound volume etc). An image without the cross hairs may also be capturedby the PDA deactivating laser 21. This may be desirable where an imageof the wound only is required. Where previous information has beenstored comparative measurements may be made and an indication ofimprovement or deterioration may be provided. Where the PDA has wirelesscapabilities images may be sent directly for storage in a centraldatabase or distributed to medical professionals for evaluation. Thisallows an expert to review information obtained in the field and providemedical direction whilst the health practitioner is visiting thepatient. The historic record allows patient progress to be tracked andre-evaluated, if necessary.

Measurements of other wound information may also be made. The colour ofthe wound and the size of particular coloured regions may also becalculated. These measurements may require a colour reference target tobe placed within the image capture area for accurate colour comparisonto be made.

According to another embodiment a 3-D camera may be employed. FIGS. 6and 7 show a tablet PC 26 having a stereoscopic 3-D camera 27 connectedthereto. Tablet PC 26 is a notebook PC with an interactive screen suchas a Toshiba Portege M200 and camera 27 may be a stereo camera such as aPoint-Grey Bumblebee camera. In this embodiment the stereoscopic camera27 provides three-dimensional image information which is utilised by thetablet PC 26 to produce a three-dimensional model. However, as in theprevious embodiments, a user utilising input device 28 may draw outline29 around the wound displayed on the tablet PC screen. Utilising thethree dimensional data, area and volume may be directly calculated.

In other embodiments “time-of-flight” cameras may be substituted forcamera 27. Time-of-flight cameras utilise modulated coherent lightillumination and per-pixel correlation hardware.

Referring now to FIGS. 8 and 9 an alternative apparatus and method willbe described. The apparatus shown in FIG. 8 includes a pair of lasers 35and 36 which project crossing fan beams 37 and 38 onto surface 39.Lasers 35 and 36 are maintained in a fixed relationship with respect toeach other and camera 40. By utilising crossing beams 37 and 38 thespacing between beams 37 and 38 may be adjusted by a user over aconvenient range by moving the assembly of lasers 35, 36 and camera 40towards or away from surface 39.

FIG. 9 illustrates use of the apparatus shown in FIG. 8 in relation to acylindrical surface 42, such as is typical for a section of an arm orleg. The method may be applied to any surface that may be transformed toa planar (flat) form, ie “unwrapped”. In the case of a “developable”surface, there is no distortion and the surface remains continuous, bydefinition. When fan beams 37 and 38 are projected onto cylindricalsurface 42 they curve in a diverging manner as shown in FIG. 9. A usermoves the assembly of lasers 35 and 36 and camera 40 with respect to thesurface 42 so as to place beams 37 and 38 just outside the boundary 41of a wound. Camera 40 then captures an image as shown in FIG. 9. Forlarger wounds the beams 37 and 38 may be within the boundary 41 of awound.

The three-dimensional locations of elements of beams 37 and 38 may thenbe determined from the captured image. A three dimensional model of thesurface (grid 43 illustrates this) may be calculated using the threedimensional coordinates of elements along lines 37 and 38. The model maybe an inelastic surface draped between the three-dimensional coordinatesof the structured light elements, or an elastic surface stretchedbetween the three-dimensional coordinates, or a model of the anatomy, orsimply a scaled planar projection. A model of the anatomy may be a modelretrieved from a library of models, or simply a geometric shapeapproximating anatomy (a cylinder approximating a leg, for example).

In a first method the three dimensional surface may be unwrapped to forma planar image in which all regions have the same scale (i.e. for a gridthe grid is unwrapped such that all cells of the image are the samesize). The area within wound boundary 41 may then be easily calculatedby calculating the area from the planar image.

Alternatively the area within wound boundary 41 may be calculated byscaling the areas within each region according to scale attributesassociated with each region (e.g. for the grid example normalising thetotal area within each cell to be the same). The granularity can ofcourse be adjusted depending upon the accuracy required.

This approach could be extended so that a plurality of parallel crossinglines are projected to achieve greater accuracy. The lines could havedifferent optical characteristics (e.g. colour) to enable them to bedistinguished. However, the two line approach described above does havethe advantage of mimicking some manual approaches currently employedwhich involves tracing the wound outline onto a transparent sheet andthen calculating the area.

FIG. 10 shows an apparatus according to a further embodiment, in whichone or more further sensors are provided. The apparatus 50 includes aPDA 51, with a housing 52 containing a camera 53, laser generator 54 anda GPS receiver 55. The GPS receiver may alternatively be provided in aseparate module, within the PDA 51 or in a plugin card. When external tothe PDA, the positioning module may be connected to the PDA via anysuitable wired or wireless connection. Positioning systems other thanGPS may also be suitable.

Use of a positioning system allows automation of tasks and validation ofactions. This may be achieved using the apparatus alone, or throughcommunication with a central computer system and database. For example,a nurse may be using the apparatus to monitor wound healing for apatient. The nurse arrives at the patient's home and the position of thehome is determined using the GPS system. The position may be used indetermining an address. This may be used to ensure that the nurse is atthe correct address, possibly by comparison with a schedule of patientvisits.

In response to determination of an address, the system may automaticallyselect a patient associated with that address from a patient database.Alternatively, for a new patient, the nurse enters patient informationusing the PDA and this information is automatically associated with theaddress determined using the GPS receiver. This avoids the necessity toenter a large amount of data using the PDA. Similarly, the position maybe used directly without converting to an address, to select a patientassociated with that position, or to associate a new patient with aposition.

The positioning system may also be used in auditing user actions. Forexample, a nurse may enter patient information and this may be verifiedusing the position data by checking it against a patient database. Thisalso allows an employer to monitor staff actions, to ensure that a staffmember has in fact visited a particular address or patient.

Data gathered using the GPS system may also be stored for futurereference. For example, travel data may be gathered by monitoringposition information over a period of time. This data may be used laterin estimating travel times between sites and in establishing oroptimizing travel schedules for workers.

FIG. 10 also shows an auxiliary sensor 56, connected to the PDA via awired connection 57. A wireless connection may also be used and anynumber of auxiliary sensors may be connected to the PDA. Auxiliarysensors could also be included in the module 52. The auxiliary sensorallows further data to be gathered. For example, where the apparatus isused to capture an image of a wound in a patient's skin, the auxiliarysensor will allow measurement of another physical or chemical parameterassociated with the patient, such as temperature, pH, moisture or odour.The auxiliary sensor may also be an optical probe, which illuminates theskin or wound and analyses the spectrum of scattered light. For example,a fluorescence probe could be used.

In one embodiment the auxiliary sensors include a Doppler UltrasoundProbe. The management of some types of wound, such as vascular ulcers,requires measurement of blood-flow in the underlying tissue and DopplerUltrasound is the method generally used to perform this measurement.Low-power Doppler Ultrasound Probes such as those used in foetalheart-beat monitors may be suitable. This would make it unnecessary fora patient to visit a clinic or hospital, or for a separate ultrasoundmachine to be transported.

Data gathered from the auxiliary sensors may be associated with aparticular address, patient or image. Data may be displayed on the PDA'sscreen, and may be overlaid on the associated image. The combinedinformation may enable more advanced wound analysis methods to beemployed.

Use of auxiliary sensors allows many measurements to be more easilyperformed at the same time as an image is captured and by the sameperson. (In a medical setting, this person may also be performing woundtreatment.) This is efficient and also allows data to be easily andaccurately associated with a particular image or patient.

In any of the above embodiments the section containing the lasers andcamera could be combined so that they can be housed in a detachable unitfrom the PDA, interfaced via a SDIO or Compact Flash (CF) slot, forexample. This allows added convenience for the user, plus enables lasersand cameras to be permanently mounted with respect to each other, forease of calibration. Furthermore, the camera can be optimally focussed,and an illumination means, such as a white LED, may be used to giverelatively constant background lighting.

In any of the above embodiments the section containing the camera and/orlasers could be movable with respect to the PDA (being interconnected bya cable or wirelessly). This allows independent manipulation of thecamera to capture wounds in awkward locations whilst optimising viewingof the image to be captured.

In any of the embodiments described above, multiple images may becaptured in rapid succession. This is particularly advantageous wherestructured light (e.g. a laser) is used. For example, two images may becaptured: one with the laser on and one with the laser off. Subtractingone of these images from the other yields an image with just the laserlines (disregarding the inevitable noise). This facilitates theautomated detection of the laser profiles. Other combinations of imagesmay also be useful. For example, three images could be captured: onewithout illumination but with the laser on, one without illumination andwith the laser off and a third image with the illumination on and thelaser off. The first two images could be used to detect the laserprofile, while the third image is displayed to the user. The firstimage, showing the laser line with the illumination off would have ahigher contrast, so that the laser line would stand out more clearly.Capturing the images in rapid succession means that the motion of thecamera between the images is negligible.

FIG. 11 shows a system including one or more portable apparatuses 60such as those described above. These apparatuses 60 may communicate viaa communication network 61 with a central server 62. Preferably theapparatuses 60 communicate wirelessly with the server 62. The centralserver 62 may utilise an external database 63 for data storage.

This centralised system allows appropriate categorising and storage ofdata for future use. For example, by mining historical data from thedatabase it is possible to analyse the efficacy of a particulartreatment or to compare different treatments. Statistical trends ofconditions, treatments and outcomes can be monitored. This data can beused to suggest a particular treatment, based on a set of symptomsexhibited by a particular patient. Data can provide predictions forwound healing. Where actual healing differs from the prediction by morethan a threshold, the system may issue an alert.

A healthcare provider can use the data to audit efficiency of its wholeorganisation, departments within the organisation or even individualworkers. Historical data may be compared with historical workerschedules to determine whether workers are performing all tasks on theirschedules. Efficiencies of different workers may be compared.

There are thus provided methods of measuring wounds that are simple,inexpensive, repeatable and may be performed remotely. The methodsutilise human image processing capabilities to minimise the processingrequirements.

The methods do not require the placement of articles near the wound andallow historical comparison of a wound. The apparatus are portable withrelatively low processing requirements and enable records to be sentwirelessly for evaluation and storage.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin detail, it is not the intention of the Applicant to restrict or inany way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, representative apparatus andmethod, and illustrative examples shown and described. Accordingly,departures may be made from such details without departure from thespirit or scope of the Applicant's general inventive concept.

1-78. (canceled)
 79. A method of producing a planar form of a non-planar surface including a surface feature comprising: a. projecting structured light onto the surface; b. capturing an image including the surface feature; c. determining the three-dimensional coordinates of structured light elements within the image; and d. unwrapping the image based on the three-dimensional coordinates of the structured light elements to produce a planar form of the surface.
 80. A method as claimed in claim 79, further comprising determining the area and/or depth of the surface feature.
 81. A method as claimed in claim 79 wherein the image is unwrapped according to either a model of an inelastic surface draped between the three-dimensional coordinates of the structured light elements, or a model of an elastic surface stretched between the three-dimensional coordinates of the structured light elements.
 82. A method as claimed in claim 79 wherein the image is unwrapped according to a model of physical anatomy.
 83. A method as claimed in claim 81 wherein the model is a developable surface model.
 84. A method of producing a projection of a surface feature comprising: a. capturing an image of a surface feature; b. determining from the image the coordinates of a plurality of points of the surface feature in three-dimensional space; c. determining a plane in which at least a subset of the coordinates lie; and d. projecting the image onto the plane to produce a transformed image.
 85. A method as claimed in claim 84 further comprising determining one or more of: the area of the surface feature from the transformed image; and the depth of at least one coordinate with respect to the plane.
 86. A method as claimed in claim 84 wherein the coordinates of a plurality of points of the surface feature are determined by projecting structured light onto the surface feature and determining the coordinates based on information from the image.
 87. A method of determining at least one dimension of a surface feature, including: a. capturing an image including a surface feature; b. determining a scale associated with the image; c. manually inputting at least part of an outline of the surface feature; and d. determining at least one dimension of the surface feature using the manually input outline data.
 88. A method as claimed in claim 87 wherein a scale associated with the image is determined by projecting structured light onto the surface feature, determining coordinates of points of the surface feature based on attributes of the structured light, determining a scale associated with the image from the coordinates.
 89. An apparatus including: a. a camera for capturing an image including a surface feature; and b. a portable computing device including: i. a display configured to display the image and to allow a user to manually input at least part of an outline of the surface feature; and ii. a processor configured to determine a scale associated with the image and to determine at least one dimension of the surface feature using the manually input outline data.
 90. An apparatus as claimed in claim 89 including a structured light projector disposed at an angle to the optical axis of the camera.
 91. A portable apparatus including: a. a camera for capturing an image of a surface feature; b. a portable computing device including a processor adapted to determine a scale associated with the image; and a. a positioning module allowing the position of the apparatus to be determined.
 92. A portable apparatus as claimed in claim 91 wherein the positioning module includes a GPS receiver.
 93. A system including a portable apparatus as claimed in claim 91, the system being configured to determine the position of the apparatus using the positioning module and to retrieve one or more of: personal details associated with the position; and address information in accordance with the position.
 94. A system as claimed in claim 93 configured to associate the image with the address and/or position and/or personal details.
 95. A healthcare apparatus including: a. a camera for capturing an image of a surface feature on a patient; b. one or more auxiliary sensors for determining a physical or chemical parameter associated with the patient; and c. a portable computing device configured to receive image data from the camera and output from the auxiliary sensors, including a processor adapted to determine a scale associated with the image.
 96. A healthcare apparatus as claimed in claim 95 wherein the auxiliary sensors include one or more of: a Doppler Ultrasound Probe; a thermometer; a pH sensor; a moisture sensor; an odour sensor; and an optical probe.
 97. A healthcare system including one or more apparatuses as claimed in claim 89, a server and a central database, wherein each portable apparatus is configured to communicate over a communications network with the server, which is adapted to receive patient data and images from the portable apparatuses and to store them in the central database, allowing historical patient data and images to be retrieved.
 98. A healthcare system as claimed in claim 97 wherein the processor or one of the apparatuses is configured to perform one or more of: processing patient data and or images retrieved from the database in order to assess the effectiveness of a particular treatment; receiving current patient data and suggesting a treatment based on that patient data and on historical patient data retrieved from the database; receiving patient data and providing one or more predictions for wound healing based on that patient data and on historical patient data retrieved from the database; and issuing an alert when actual wound healing differs from the predictions by more than a threshold.
 99. An apparatus including: a. a camera for capturing an image including a surface feature; and b. one or more structured light projectors configured to project structured light onto the surface, the structured light including two or more structured light components, each projected at a different angle to the camera's optical axis.
 100. An apparatus as claimed in claim 99 further including a portable computing device having a processor, wherein the structured light components are three or more spots projected onto the surface, and the processor is configured to fit a plane through at least three points where the spots lie on the surface.
 101. An apparatus as claimed in claim 99 wherein the structured light components are stripes projected onto the surface.
 102. An apparatus as claimed in claim 101 wherein the structured light components include a first stripe and a second stripe projected so as cross before reaching the surface.
 103. An apparatus as claimed in claim 101 further including a portable computing device having a processor, wherein the processor is configured to map the surface feature into a plane based on the positions of the stripes on the surface. 